It's probably not the right project if you do not know how to even get started.
But to give you a chance:
- check out CMS-Systems. Content Managment Systms are used to make hompages and have modular structure to give extra functionality. I would suggest Joomla
]. Extensions are easy to be made there.
- Then I would figure out some connection to the mobile. That usually involves some kind of phone line...
- The last part is the MMS. You need to figure out the format and how to create that.
A simple search on Google presented me JMMSlib @ sourceforge.net
]. I would expext that to be helpful.
Now to YOUR WORK
- project plan
- structure (time & function)